<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>lesson4_2bug</title>
		<link rel="stylesheet" type="text/css" href="css/lesson4_2bug.css"/>
	</head>
	<body>
		<!--1.margin塌陷-->
		<!--bfc(block format context)
			触发bfc:
				1.position:absolute;
				2. display: inline-block;
				3.float:left/rigth;
				4.overflow:hidden; 溢出部分影藏
		-->
		<!--<div class="wrapper">
			<div class="content"></div>
		</div>-->
		<!--========================line1============================-->
		<!--2.margin合并
			1.包括层
			2.不解决 计算
			bfc
		-->
		<!--<span class="box1">123</span>
		<span class="box2">234</span>
		<div class="demo1">1</div>
		<div class="demo2">2</div>-->
	</body>
</html>
